Dishwasher Air Gap

Many community plumbing codes around the country require a backflow preventer on builtin dishwashers. That chrome "thingamajig" sitting on the edge of the kitchen sink next to your faucet or protruding from the wall over the sink is an air gap. That "whatyamacallit" prevents wastewater from flowing back into the dishwasher from the garbage disposer or the sink drain. It is not an overflow; water or suds should not flow out of it.

Periodically, you should remove the air gap cover, unscrew the cap and clean it out. The covers usually lift off, but some unscrew. Toothpicks, fish bones and such things as watermelon seeds will lodge inside the air gap and block the water draining from the dishwasher and force water and suds out through the air gap slots.

If you do a good job of scraping dishes before putting them in the dishwasher, you may never have a problem, but if your dishwasher is slow to drain, or suds bubbly out of the air gap, check that air gap before you call for repairs.

If cleaning out the air gap doesn't solve the problem, the clog may be inside the end of the drain line where it connects to the garbage disposer. The dishwasher drain opening is just below the rubber flange inside the mouth of the garbage disposer. Now don't put your hand inside the garbage disposer, unless you're certain it can't be turned on, but you can usually loosen debris stuck in the drain opening with a stiff wire.

Gently ream out the opening to loosen the clog and then turn the dishwasher on. The force of the water draining from the dishwasher should clear the line. If not, take a long stiff but flexible wire and run it down into opening of the air gap until it comes out inside the garbage disposer

If this doesn't work, you'll have to disconnect the drain hose under the sink at the point where it attaches to the drain or disposer in order to clean out the hose.